1. Field of the Invention
The present invention relates to methods and apparatuses for causing electroluminescence with charge trapping structures. Embodiments of the present invention relate to methods and apparatuses for causing electroluminescence with charge carriers of one type provided to the charge trapping structure from a forward biased p-n structure or from a reverse biased p-n structure.
2. Description of Related Art
Electroluminescent devices emit photons by exciting material with electric field or current. Conventional silicon-based electroluminescent devices have low efficiency due to the indirect bandgap of silicon. Because of the indirect bandgap, prior to recombination between an electron and a hole, the momentum mismatch must be corrected, leading to the low efficiency. The low efficiency in turn results in low light density. One approach that addresses this momentum mismatch is by diverging the k-space through physical confinement in very small silicon quantum dots. However, the processing for making silicon dots sufficiently small is difficult and expensive.
Direct bandgap-based electroluminescent devices materials do not have the momentum mismatch issues associated with conventional silicon-based devices. However, many direct bandgap materials such as GaAs are more difficult to integrate with silicon, which has significant cost advantages and remains the material of choice for many more applications.
Conventional trapping material-based electroluminescent devices are relatively easy to integrate with silicon-based technologies such as CMOS. However, there are limitations to the electron and hole energies permitted by conventional trapping material-based electroluminescent devices. Because the transport mechanism for both electrons and holes into the charge trapping material is diffusion from a neighboring material such as a gate or the substrate, the energies of recombining holes and electrons are low due to collisions and phonon scattering, and the recombination events between these holes and electrons result in low energy photons. Also, the electron/hole recombination rate in the trapping material is small, because of the poor diffusion rates of electrons and holes in the trapping material.